1. Field of the Invention
The invention relates to a degree-of-supercooling control type expansion valve upstream of an evaporator in a refrigerating cycle and containing a valve seat, a valve body, a throttling portion and a force exerting means biasing said valve body towards said valve seat, according to the preamble part of claim 1 and to the preamble part of independent claim 2.
A conventionally used expansion valve in a refrigerating cycle is a so-called temperature type expansion valve controlling the discharge of a refrigerant entering an evaporator in response to the temperature and the pressure of a low-pressure refrigerant discharge from the evaporator.
2. Description of the Related Art
Instead of a temperature type expansion valve and disclosed in Laid-Open JP-application SHO 56-7959 an expansion valve of a degree-of-supercooling control type can be used. Said expansion valve is designed with a simple configuration and is able to constantly control the degree-of-supercooling of the high-pressure refrigerant. This allows to achieve a very simple, compact configuration of the valve and the refrigerating cycle. However, said known expansion valve of the degree-of-supercooling control type has a drawback because the degree-of-supercooling cannot be adjusted finely when the valve is assembled, which degree-of-supercooling, however, must be kept constant, e.g. in a series of production of a identical valves of said type.
It is an object of the present invention to provide an expansion valve of the degree-of-supercooling control type which can be finely adjusted when being assembled in order to keep the degree-of-supercooling of a high-pressure refrigerant constant and without losing the simplicity and compactness of the construction.
The above-mentioned object can be achieved by providing an exerting force adjusting member for finely adjusting the exerting force and by forming either the throttling portion or the valve seat structurally with the exerting force adjusting member. Said exerting force adjusting member is provided such that it allows to adjust the exerting force either during assembly or even after assembly of the expansion valve in a series of such expansion valve having identical structural features. Said adjustment can be carried out in order to keep the degree-of-supercooling of a high-pressure refrigerant constant, e.g. among a series of identical expansion valves.
In case that said exerting force adjusting member simultaneously is forming said valve seat, it does indirectly support said force exerting means via said valve body.
In case that said exertion force adjustment member simultaneously is forming said valve seat, said throttling portion is formed with said valve body co-operating with said valve seat. In both cases said exerting force adjusting member is carrying out a dual function, while in the second case even the valve body is carrying out a dual function. As a result the overall design is simplified. The dimensions of the expansion valve can be kept compact.
Alternatively, with said valve seat formed with said exerting force adjusting member said counterfort is formed with said throttling portion. Also in this case, both components carry out dual function.
Alternatively, with said throttling portion formed with said exerting force adjusting member said counterfort is formed with said valve seat. Again, said counterfort and said force exerting adjusting member fulfil dual functions and allow to achieve a compact and structurally simple design.
According to a further aspect of the invention both said exerting force adjusting member and said counterfort are formed with a respective valve seat and two opposed valve bodies are associated to both valve seats so that both valve bodies are biased in opposite directions by a common force exerting means and both valve bodies being formed with respective throttling portions. In this case both valve seats are located oppositely with a certain intermediate distance between them. A controlled flow in both directions is possible, which might be desirable e.g. for a refrigerating cycle also used as a heating cycle. This design results in a bi-directional expansion valve.
In the latter case it is desirable to have check valves restricting the inflow of refrigerant from the external side into the expansion valve. Structurally simple said check valves are integrated into the throttling portions wherein the throttle openings simultaneously constitute valve seats for the check valves.
Said force exerting means can be at least one spring. Advantageously, said spring is made from a shape memorising alloy providing a temperature depending variable spring constant. Of particular advantage is if the spring is responsive to a temperature rise in the refrigerant by a spring constant increase. This leads to the positive effect that the degree-of-supercooling as controlled constantly increases when a load for the refrigerating cycle is large and consequently the temperature of the refrigerant starts to rise. Thereby, the cooling power increases permitting the adaptation of the cooling effect to the outside condition.
Expediently the force exerting adjusting member is threadably received in the refrigerant passage. This allows to gradually adjust the exerting force or to steplessly vary the pre-load of the force exerting means.
Alternatively, said exerting force adjusting member can be positioned by a press-fit in axial direction within the refrigerant passage in the proper position in order to adjust the exerting force to a desired value.
Finally, said throttling portion, which conventionally is a through bore, instead may be shaped with an annular or ring-shaped cross-section. Having the same throttling factor across the throttling portion a ring-shaped throttling portion is providing an enlarged contact surface for the refrigerant leading to the positive effect of a greatly reduced passing sound of the refrigerant. A ring-shaped throttling portion avoids the formation of an undesirable operation noise source. Said ring-shaped cross-section can be formed by discrete ring segments or with a continuous ring shape.